Both retinal and choroidal vessels are necessary for proper retinal function in man, however, only the retinal vessels are readily visible to the ophthalmologist. Fluorescein angiography provides further information concerning the retinal circulation and also some information regarding choroidal circulation and retinal pigment epithelial integrity. These 2 methodologies, i.e., ophthalmoscopy and fluorescein angiography, are of primary importance in the clinical interpretation of vascular-neural cell interrelationships in retinal disease. We propose to study the role of the retinal and choroidal vasculature in the pathogenesis of 3 experimental retinopathies in 1 species, the laboratory rat. These are (1) urethan induced, (2) hereditary dystrophic, and (3) phototoxic retinopathy. Although of different etiologies all 3 retinopathies have vascular abnormalities in association with visual cell degeneration and pigment epithelial cell disturbance. We will utilize the in vivo techniques of ophthalmoscopy, fundus photography, and fluorescein angiography and correlate that information with findings derived from the in vitro techniques of light and electron microscopy, biochemistry, and histochemistry. Comparison of data obtained is enhanced by studying only 1 species. Careful comparison of the development of vessel alterations with concurrent neural cell changes may elucidate determinants of vessel response in the presence of neural cell damage. Our objective is to understand more fully the role of retinal and choroidal circulation in retinopathies, and these experimental animal studies should provide meaningful information applicable to interpreting vascular-neural cell interrelationships in retinal disease in man.